Hundreds of resources searchable by key stage and subject.
Resource site with lots of interactive games and video clips. Need to register.
Teach it Science is a subscription resources site, however if you register you can access PDF files free of charge, there are worksheets here for many topics in KS3 and KS4 for all three sciences.
Resources submitted by teachers – search by subject and Key Stage.
Has interactive activities for various science units at primary and secondary.
Resources from North Chadderton school – includes lesson plans and powerpoints for KS3, KS4 and A level as well as images for using in projects or presentations.